Abstract:

Green electrochromic (EC) materials based on thiophene, and a green EC
material based on pyrazine are disclosed. A first thiophene derivative
(2,3-Di-thiophen-2-yl-thieno[3,4-b]pyrazine), which was previously
investigated as a nonlinear optical material, is here disclosed for its
use as an EC material and for its incorporation into an EC device.
Synthesis of two new thiophene derivatives
(2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene and
2,5-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-3,4-di(2,2,2-trifluoro-et-
hoxy)-thiophene), and a new pyrazine derivative
(2,3-dibenzyl-5,7-di(thien-2-yl) thieno[3,4-b]pyrazine) are also
disclosed, since these materials are all able to selectively change state
to appear a green color and can be polymerized to achieve a green EC
polymer.

Claims:

1. A method for synthesizing a desired product, the desired product
comprising 2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoroethoxy)-thiophene, a
monomer suitable for polymerization to achieve a fluorinated
electrochromic polymer exhibiting a green color in a first state and a
red color in a second state, the method comprising the steps of:(a)
producing a first intermediate reagent, the first intermediate reagent
comprising 2,5-dibromo-3,4-bis-(2,2,2-trifluoroethoxy)-thiophene, by:(i)
providing a first solution comprising a first precursor, the first
precursor comprising 3,4-bis-(2,2,2-trifluoroethoxy)-thiophene; and(ii)
heating the first solution to facilitate a reaction that produces the
first intermediate reagent; and(b) producing the desired product by
heating a second solution comprising the first intermediate reagent and a
substituted thiophene, to facilitate a reaction that produces the desired
product.

2. The method of claim 1, wherein:(a) the first solution further comprises
N-bromosuccinimide, chloroform and acetic acid;(b) the substituted
thiophene comprises 2-tributyltin thiophene, and the second solution
further comprises a palladium catalyst and tetrahydrofuran; and(c) the
second solution is heated for substantially longer than the first
solution.

3. The method of claim 1, wherein:(a) the first solution is heated for a
period of time ranging from about 15 minutes to about 45 minutes; and(b)
the second solution is heated for about 15 hours.

4. The method of claim 1, wherein:(a) the step of heating the first
solution comprises the step of refluxing the first solution under an
inert atmosphere; and(b) the step of heating the second solution
comprises the step of refluxing the second solution under an inert
atmosphere.

5. The method of claim 1, further comprising the steps of:(a) purifying
the first intermediate reagent using chromatography; and(b) purifying the
desired product using chromatography.

6. The method of claim 1, further comprising the step of dissolving the
first precursor into the first solution by stirring the first solution
for an extended period of time.

7. The method of claim 1, further comprising the step of producing the
first precursor by:(a) providing a third solution comprising a second
precursor, the second precursor comprising
3,4-bis-(2,2,2-trifluoroethoxy)-thiophene-2,5-dicarboxylic acid; and(b)
heating the third solution to facilitate a reaction that will produce the
first precursor.

8. The method of claim 7, wherein:(a) the third solution further comprises
quinoline and a barium promoted copper chromite catalyst;(b) the third
solution is heated for substantially longer than the first solution;(c)
the third solution is heated for a period of time ranging from about
12-18 hours;(d) the third solution is heated to about 170-190.degree.
C.;(e) the first precursor is purified before being used to produce the
first intermediate reagent; and(f) the third solution is heated under an
inert atmosphere.

9. The method of claim 7, further comprising the step of producing the
second precursor by:(a) providing a fourth solution comprising a third
precursor, the third precursor comprising
3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene-2,5-dicarboxylic acid dimethyl
ester; and(b) heating the fourth solution to facilitate a reaction that
will produce the second precursor.

10. The method of claim 9, wherein:(a) the fourth solution further
comprises sodium hydroxide and ethanol;(b) the fourth solution is heated
for substantially longer than the first solution;(c) the fourth solution
is heated for a period of time ranging from about 12-20 hours;(d) the
fourth solution is heated to about 50-70.degree. C.;(e) the second
precursor is purified before being used to produce the first
precursor;(f) the step of heating the fourth solution comprises the step
of stirring while heating; and(g) the step of heating the fourth solution
comprises the step of heating the fourth solution under an inert
atmosphere.

11. The method of claim 9, further comprising the step of neutralizing any
sodium hydroxide in the fourth solution using an acid after the solution
has been heated.

12. The method of claim 9, further comprising the step of producing the
third precursor by:(a) providing a fifth solution comprising a fourth
precursor and 2,2,2-trifluoroethanol, the fourth precursor comprising
3,4-dihydroxy-thiophene-2,5-dicarboxylic acid dimethyl ester; and(b)
heating the fifth solution to facilitate a reaction that will produce the
third precursor.

13. The method of claim 12, wherein:(a) the fifth solution further
comprises triphenylphosphine (PPh3), tetrahydrofuran and diethyl
azodicarboxylate (DEAD);(b) the fifth solution is heated for
substantially longer than the first solution;(c) the fifth solution is
heated for a period of time ranging from about 15-24 hours;(d) the third
precursor is purified before being used to produce the second precursor;
and(e) the step of heating the fifth solution comprises the step of
refluxing the fifth solution under an inert atmosphere.

14. The method of claim 13, wherein the third precursor is purified by
evaporating the fifth solution to dryness to generate a solid reaction
product, and eluding the third precursor from the solid reaction product
using hexane and dichloromethane.

15. A method for synthesizing a fluorinated electrochromic monomer
suitable for polymerization to achieve a fluorinated electrochromic
polymer, the fluorinated electrochromic monomer being a fluorinated
derivative of 2,5-di(thien-2-yl)-3,4-dihydroxy-thiophene, the fluorinated
derivative corresponding to 2,5-di(thien-2-yl)-3,4-di(R-oxy)-thiophene,
with R comprising a fluorinated functional group, the method comprising
the steps of:(a) producing a first intermediate reagent comprising a
fluorinated derivative of 3,4-dihydroxy-thiophene-2,5-dicarboxylic acid
dimethyl ester, the fluorinated derivative corresponding to
3,4-bis-(R-oxy)-thiophene-2,5-dicarboxylic acid dimethyl ester, by
performing the steps of:(i) providing a first solution comprising
3,4-dihydroxy-thiophene-2,5-dicarboxylic acid dimethyl ester and a
fluorinated alcohol comprising R, the fluorinated functional group;
and(ii) heating the first solution to facilitate a reaction that will
produce the first intermediate reagent;(b) producing a second
intermediate reagent comprising a fluorinated derivative of
3,4-dihydroxy-thiophene-2,5-dicarboxylic acid, the fluorinated derivative
corresponding to 3,4-bis-(R-oxy)-thiophene-2,5-dicarboxylic acid, by
performing the steps of:(i) adding the first intermediate reagent to a
second solution; and(ii) heating the second solution to facilitate a
reaction that will produce the second intermediate reagent;(c) producing
a third intermediate reagent comprising a fluorinated derivative of
3,4-dihydroxy-thiophene, the fluorinated derivative corresponding to
3,4-bis-(R-oxy)-thiophene, by performing the steps of:(i) adding the
second intermediate reagent to a third solution; and(ii) heating the
third solution to facilitate a reaction that will produce the third
intermediate reagent;(d) producing a fourth intermediate reagent
comprising a fluorinated derivative of
2,5-dibromo-3,4-dihydroxy-thiophene, the fluorinated derivative
corresponding to 2,5-dibromo-3,4-bis-(R-oxy)-thiophene, by performing the
steps of:(i) adding the third intermediate reagent to a fourth solution;
and(ii) heating the fourth solution to facilitate a reaction that will
produce the fourth intermediate reagent; and(e) using the fourth
intermediate reagent to produce the fluorinated derivative of
2,5-di(thien-2-yl)-3,4-dihydroxy-thiophene by:(i) adding the fourth
intermediate reagent to a fifth solution comprising a substituted
thiophene; and(ii) heating the fifth solution to facilitate a reaction
that will produce the fluorinated derivative of
2,5-di(thien-2-yl)-3,4-dihydroxy-thiophene.

16. The method of claim 15, wherein the fluorinated alcohol is selected
from a group consisting of 2,2,2-trifluoroethanol, 2-fluoroethanol,
2,3,4,5,6-pentfluorobenzyl alcohol, and 2,2-difluoro-1,3-propanediol.

17. The method of claim 15, wherein the first, fourth and fifth solutions
are refluxed during heating.

18. The method of claim 15, wherein:(a) the first solution further
comprises triphenylphosphine (PPh3), tetrahydrofuran and diethyl
azodicarboxylate (DEAD);(b) the second solution comprises sodium
hydroxide and ethanol;(c) the third solution comprises quinoline and a
barium promoted copper chromite catalyst;(d) the fourth solution
comprises N-bromosuccinimide, chloroform and acetic acid; and(e) the
substituted thiophene comprises 2-tributyltin thiophene, and the fifth
solution further comprises a palladium catalyst and tetrahydrofuran.

19. A method for synthesizing a desired product, the desired product
comprising
2,5-(2,3-dihydro-thieno[3,4][1,4]dioxin-5-yl)-3,4-di(2,2,2-trifluoroethox-
y)-thiophene, a monomer suitable for polymerization to achieve a
fluorinated electrochromic polymer exhibiting a green color in a first
state and a purple color in a second state, the method comprising the
steps of:(a) providing a first solution comprising a first intermediate
reagent and a second intermediate reagent, the first intermediate reagent
comprising 2,5-dibromo-3,4-bis-(2,2,2-trifluoroethoxy)-thiophene, and the
second intermediate reagent comprising a substituted ethylenedioxyl
thiophene; and(b) heating the first solution to facilitate a reaction
that will produce the desired product.

Description:

RELATED APPLICATIONS

[0001]This application is a divisional of a copending patent application
Ser. No. 11/876,513, filed on Oct. 22, 2007, which itself is a
continuation-in-part of copending patent application Ser. No. 11/774,438,
filed Jul. 6, 2007, now U.S. Pat. No. 7,505,191, and Ser. No. 11/223,794,
filed on Sep. 9, 2005, now U.S. Pat. No. 7,298,541. patent application
Ser. No. 11/223,794 is based on a prior copending provisional application
Ser. No. 60/608,438, filed on Sep. 9, 2004. In addition, patent
application Ser. No. 11/223,794 is also a continuation-in-part of a
copending patent application Ser. No. 11/070,392, filed on Mar. 1, 2005,
now U.S. Pat. No. 7,256,923,which itself is based on a prior copending
provisional application Ser. No. 60/549,035, filed on Mar. 1, 2004.
patent application Ser. No. 11/070,392 is also a continuation-in-part of
a copending patent application Ser. No. 10/917,954, filed on Aug. 13,
2004, now U.S. Pat. No. 7,450,290, which itself is based on two prior
copending provisional applications, Ser. No. 60/495,310, filed on Aug.
14, 2003, and Ser. No. 60/523,007, filed on Nov. 18, 2003. Copending
patent application Ser. No. 10/917,954 is also a continuation-in-part of
a copending patent application Ser. No. 10/755,433, filed Jan. 12, 2004,
now U.S. Pat. No. 7,002,722, which in turn is a divisional of an earlier
patent application Ser. No. 10/180,222, filed Jun. 25, 2002, now U.S.
Pat. No. 6,747,780. The benefit of the filing dates of these related
applications is hereby claimed under 35 U.S.C. §§119(e) and
120.

BACKGROUND

[0002]Electrochromic (EC) materials are a subset of the family of
chromogenic materials, which includes photochromic materials, and
thermochromic materials. These materials change their tinting level or
opacity when exposed to light (photochromic), heat (thermochromic), or an
electric potential (electrochromic). Chromogenic materials have attracted
widespread interest in applications relating to the transmission of
light.

[0003]An early application for the use of chromogenic materials was in
sunglasses or prescription eyeglasses that darken when exposed to the
sun. Such photochromic materials were first developed by researchers at
Corning Incorporated in the late 1960s. Since that time, it has been
recognized that chromogenic materials could potentially be used to
produce window glass that can vary the amount of light transmitted,
although the use of such materials is clearly not limited to that
prospective application. Indeed, EC technology is already employed in the
displays of digital watches.

[0004]Several different distinct types of EC materials are known. Three
primary types are: inorganic thin films, organic polymer films, and
organic solutions. For many applications, the use of a liquid material is
inconvenient, and as a result, inorganic thin films and organic polymer
films appear to have more industrial applications.

[0005]For inorganic thin film-based EC devices, the EC layer is typically
tungsten oxide (WO3). U.S. Pat. Nos. 5,598,293; 6,005,705; and
6,136,161 describe an inorganic thin film EC device based on a tungsten
oxide EC layer. Other inorganic EC materials, such as molybdenum oxide,
are also known. While many inorganic materials have been used as EC
materials, difficulties in processing and a slow response time associated
with many inorganic EC materials have created the need for different
types of EC materials.

[0006]Conjugated, redox-active polymers represent one different type of EC
material. These polymers (cathodic or anodic polymers) are inherently
electrochromic and can be switched electrochemically (or chemically)
between different color states. A family of redox-active copolymers is
described in U.S. Pat. No. 5,883,220. Another family of nitrogen based
heterocyclic organic EC materials is described in U.S. Pat. No.
6,197,923. Research into still other types of organic film EC materials
continues, in hopes of identifying or developing EC materials that will
be useful in EC windows. There still exists room for improvement and
development of new types of EC organic polymer films, and methods of
making EC organic polymer films. For example, it would be desirable to
develop EC organic polymer films and methods for making such materials
that provide certain desirable properties, such as specific colors,
long-term stability, rapid redox switching, and large changes in opacity
with changes of state.

SUMMARY

[0007]This application specifically incorporates by reference the
disclosures and drawings of each patent application and issued patent
identified above as a related application.

[0008]Disclosed herein are several concepts related to green EC polymer
materials. A first aspect of the concepts disclosed herein is an EC
device including a green EC polymer, which exhibits its green color due
to the presence of a single absorption band.

[0009]There are two basic reasons why a material will exhibit a green
color. The first reason is based on the principle of complementary
colors. Three pairs of complementary colors are red/green, blue/orange,
and yellow/purple. If a material absorbs red light (with a wavelength of
approximately 620 nm to 780 nm) from white light, the material exhibits a
green color. The disclosure provided herein encompasses several different
materials exhibiting a single absorption peak between 620 nm and 780 nm
(i.e., materials which are green because their single absorption band
absorbs red light, the complementary color for green). A second reason
why a material will exhibit a green color is if the material includes two
different absorption bands, a first absorption band that absorbs light
with a wavelength less than about 480 nm (i.e., violet and blue light),
and a second absorption band that absorbs light with a wavelength above
about 530 nm (i.e., yellow, orange, and red light). Only green light will
be left after this subtraction of the other colors, and such materials
will exhibit a green color. The disclosure provided herein encompasses
several different materials exhibiting dual absorption peaks, which
absorb all colors but green.

[0010]A second aspect of the concepts disclosed herein is a heretofore
unknown synthesis for
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene, a green EC
monomer based on thiophene. A detailed description of the synthesis of
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene is provided
below.

[0011]A third aspect of the concepts disclosed herein is a method for
polymerizing 2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene,
using either cyclic voltammetry or a combination of chronoamperometry and
cyclic voltammetry. A detailed description of the polymerization of
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene is provided
below.

[0012]A fourth aspect of the concepts disclosed herein is a modification
of the synthesis for
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene, enabling the
2,2,2-trifluoro functional group to be replaced with a different fluorine
containing functional group. A detailed description of this alternative
synthesis is provided below.

[0013]A fifth aspect of the concepts disclosed herein is a heretofore
unknown synthesis for yet another thiophene derivative,
2,5-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-3,4-di(2,2,2-trifluoro-et-
hoxy)-thiophene. A detailed description of the synthesis of
2,5-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-3,4-di(2,2,2-trifluoro-et-
hoxy)-thiophene is also provided below.

[0014]A sixth aspect of the concepts disclosed herein is a modification of
the synthesis for
2,5-(2,3-dihydro-thieno[3,4-b][1,4]-dioxin-5-yl)-3,4-di-(2,2,2-trifluoro--
ethoxy)-thiophene, enabling the 2,2,2-trifluoro functional group to be
replaced with a different fluorine-containing functional group. A
detailed description of this alternative synthesis is provided below.

[0015]A seventh aspect of the concepts disclosed herein is a method for
polymerizing
2,5-(2,3-dihydro-thieno[3,4-b][1,4]-dioxin-5-yl)-3,4-di-(2,2,2-trifluoro--
ethoxy)-thiophene, using cyclic voltammetry. A detailed description of
this polymerization is provided below.

[0016]An eighth aspect of the concepts disclosed herein is a heretofore
unknown synthesis for a green EC material, which exhibits a green color
due to two absorption peaks, and is a pyrazine derivative,
2,3-dibenzyl-5,7-di(thien-2-yl) thieno[3,4-b]pyrazine. A detailed
description of the synthesis 2,3-dibenzyl-5,7-di(thien-2-yl)
thieno[3,4-b]pyrazine is provided below.

[0017]This Summary has been provided to introduce a few concepts in a
simplified form that are further described in detail below in the
Description. However, this Summary is not intended to identify key or
essential features of the claimed subject matter, nor is it intended to
be used as an aid in determining the scope of the claimed subject matter.

DRAWINGS

[0018]Various aspects and attendant advantages of one or more exemplary
embodiments and modifications thereto will become more readily
appreciated as the same becomes better understood by reference to the
following detailed description, when taken in conjunction with the
accompanying drawings, wherein:

[0029]FIG. 9 schematically illustrates the synthesis of Compound 1 of FIG.
7A, which may be beneficially employed as a green EC polymer, once it has
been polymerized;

[0030]FIG. 10A schematically illustrates the synthesis of Compound 3 of
FIG. 7c, which may potentially be employed as a green EC polymer, once it
has been polymerized;

[0031]FIG. 10B graphically illustrates transmittance data for Compound 3
of FIG. 7c, in both its oxidized and reduced states;

[0032]FIG. 11A (Prior Art) illustrates the structure of known materials
exhibiting a green color based on dual absorption bands, which served as
a basis for investigating new materials to identify candidates for a
dual-band green EC polymer;

[0033]FIG. 11B illustrates the structure of six newly synthesized
compounds developed while attempting to produce a dual-band green EC
polymer;

[0034]FIG. 12 schematically illustrates the synthesis of Compound 13 of
FIG. 11B, which may potentially be employed as a green EC polymer, once
it has been polymerized;

[0035]FIG. 13 is a flowchart showing exemplary logical steps executed in a
first electropolymerization technique for producing EC polymer films from
monomers;

[0036]FIG. 14 is a flowchart illustrating exemplary logical steps executed
in a second electropolymerization technique for producing EC polymer
films from monomers;

[0039]Exemplary embodiments are illustrated in referenced Figures of the
drawings. It is intended that the embodiments and Figures disclosed
herein are to be considered illustrative rather than restrictive. No
limitation on the scope of the technology and of the claims that follow
is to be imputed to the examples shown in the drawings and discussed
herein. Further, it should be understood that any feature of one
embodiment disclosed herein can be combined with one or more features of
any other embodiment that is disclosed, unless otherwise indicated.

[0040]Particularly with respect to the synthesis methods disclosed herein,
it should be noted that the times indicated in the methods disclosed are
intended to be exemplary, rather than limiting. For example, a step of
refluxing a solution for 30 minutes can be considered to be refluxing for
a relatively shorter period of time, while a step of refluxing a solution
for 17 hours can be considered to be refluxing for a relatively longer
time (or refluxing for an extended period). It should be recognized that
the concepts disclosed herein encompass longer and shorter times than
those provided as exemplary times. Similarly, quantities of reagents are
also intended to be exemplary. Further, where a particular solvent,
catalyst or other reagent is named, it must be recognized that equivalent
reagents (i.e., similar solvents, catalysts or reagents) can often be
substituted without substantially affecting the product being
synthesized.

[0041]Exemplary embodiments are illustrated in referenced Figures of the
drawings. It is intended that the embodiments and Figures disclosed
herein are to be considered illustrative rather than restrictive.

[0042]As noted above, materials exhibiting a green color can either
exhibit a single absorption peak between about 620 nm and about 780 nm,
or instead, exhibit two different absorption bands, a first absorption
band that absorbs light with a wavelength less than about 480 nm (i.e.,
violet and blue light), and a second absorption band that absorbs all
light with a wavelength above about 530 nm (i.e., yellow, orange, and red
light). FIG. 1A graphically illustrates a typical absorption spectrum of
green material exhibiting a single absorption peak, while FIG. 1B
graphically illustrates a typical absorption spectrum of green material
exhibiting dual absorption peaks.

First Exemplary Green EC Material Exhibiting a Single Absorption Peak

[0043]A first exemplary green material exhibiting a single absorption peak
that can be used as a green EC polymer is a thiophene derivative,
2,3-di-thiophen-2-yl-thieno[3,4-b]pyrazine, which originally was
evaluated for use as a nonlinear optical material. FIG. 2 illustrates the
chemical structure of a thiophene derivative 10 in both a neutral state
and in a charged state. In the neutral state, thiophene derivative 10
exhibits a very slight yellow color. Thiophene derivative 10 can be
reduced to a radical ion, which has an absorption peak at about 680 nm
and exhibits a very saturated green color. The transition from the
radical ion (dark green) to the neutral state (pale yellow) is
reversible, indicating that thiophene derivative 10 can be used as a
green EC material.

[0044]FIG. 3 schematically illustrates the synthesis of the thiophene
derivative of FIG. 2. This synthesis route was developed while conducting
research regarding the potential of the thiophene derivative for use as a
nonlinear optical material. Significantly, this research did not involve
investigating the use of thiophene derivative 10 as an EC material. As
indicated in FIG. 3, thiophene is treated with NBS to yield
2,5-dibromothiophene, which is then treated with a mixture of nitric and
sulfuric acids. The resulting 2,5-dibromo-3,4-dinitro-thiophene is
treated with tin and HCl to yield 3,4-diamino-thiophene. The
diamino-thiophene is combined with 1,2-di-thiophen-2-yl-ethane-1,2-dione
in the presence of heat to yield
2,3-di-thiophen-2-yl-thieno[3,4-b]pyrazine.

[0045]A first empirical electrochromic device was fabricated and includes
two indium tin oxide (ITO) glass slides (functioning as transparent
electrodes), a silver foil reference electrode, thiophene derivative 10,
an electrolyte (tetrabutylammonium hexafluorophosphate), and a
non-aqueous solvent (either acetonitrile or propylene carbonate). The
completed device is readily switched between a saturated green state and
a generally transparent light yellow state by a power source ranging from
about -2 volts to about 0 volts. This empirical study verified that
thiophene derivative 10 can be used to fabricate an EC device in which a
color change of the device is from substantially transparent to a
saturated green. This device is shown in FIGS. 4A and 4B. Note that
thiophene derivative 10 is dissolved in a liquid electrolyte in this
example.

[0046]A second empirical EC device was constructed to further study
thiophene derivative 10 as a green EC material. The second empirical EC
device did not incorporate a reference electrode. Instead, a charge
balancing molecule, 5,10-dihydro-5,10,dimethylphenazine, was added to
reduce the operation potential of the second empirical EC device. The
second empirical EC device was switched between states by a potential
difference as low as 1.2 volts. The switching speed between states was as
fast as 0.4 seconds. Fabrication of the second empirical EC device was
simple, because the reference electrode of the first empirical EC device
was eliminated. Preliminary results showed that the second empirical EC
device has a long cycle life, easy operation, and provides a vibrant
color. The second empirical device is schematically illustrated in FIGS.
5A and 5B. FIG. 5C graphically illustrates transmittance data for the EC
polymer device of FIGS. 5A and 5B in the oxidized and reduced states.

[0047]Note that, as indicated above, a charge balancing molecule is
incorporated into the electrolyte layer of the second empirical EC device
to reduce the switching potential. FIG. 6 schematically illustrates the
structure of the charge balancing molecule, and its redox mechanism,
which facilitates charge balancing.

Design Considerations for One-Band Green EC Materials

[0048]In order to achieve a conducting polymer that absorbs red light
(preferably exhibiting a maximum absorption around 750 nm), the
conducting polymer must have a band gap at about 1 electron volt or
lower. Such conducting polymers include low band gap polymers (also known
as "small band gap," or "narrow band gap" polymers). Several strategies
can be implemented to synthesize low band gap polymers, including
alternating the length of the conjugated structure, and introducing
electron donating and withdrawing groups into the structure. A plurality
of green EC materials have been developed using the above-identified
synthesis strategies. Several materials were identified, which exhibited
a green color in one state, and a different substantially nontransparent
color in a second state. Such materials are less desirable than EC
materials that exhibit a green color in a first state and a substantially
transparent color in a second state. Other materials were synthesized as
monomers, but proved difficult to polymerize. Several materials did
exhibit the desired color transition (i.e., from a generally transparent
state to a green state) and were successfully polymerized.

[0049]FIGS. 7A-7F schematically illustrate the structure of materials
investigated to identify candidates for a single band green EC polymer.
Compound 1, whose structure is provided in FIG. 7A, was successfully
polymerized, and exhibited a color change from red to green (although the
non-green color state is red and not substantially transparent, an EC
polymer switching between red and green color state will be potentially
useful, because some displays function by switching pixels between red,
blue, and green states). Empirical testing indicates that the monomer is
stable, and the colors exhibited by the polymer are aesthetically
acceptable.

[0050]Compound 2, whose structure is provided in FIG. 7B, exhibited the
desirable color change of substantially colorless to green; however,
Compound 2 was not successfully polymerized.

[0051]Compound 3, whose structure is provided in FIG. 7c, was successfully
polymerized, and exhibited a color change from purple to green.

[0052]Compound 4, whose structure is provided in FIG. 7D, was successfully
polymerized, and exhibited a color change from orange to dark green.

[0054]Compound 6, whose structure is provided in FIG. 7F, was successfully
polymerized, and exhibited a color change from dark gray to green.
Testing determined that Compound 6 is not electrochemically stable.

[0055]Based on the results of the study noted above, it was determined
that Compound 1 and Compound 3 warranted further evaluation. FIG. 8
graphically illustrates transmittance data for Compound 1, the structure
of which is shown in FIG. 7A, in both the oxidized and reduced states.

Exemplary Synthesis for Compound 1 (FIG. 7A)

[0056]FIG. 9 schematically illustrates the synthesis of Compound 1 (i.e.,
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene), the
structure of which is shown in FIG. 7A, which may be beneficially
employed as a green EC polymer once it has been polymerized.

[0057]Synthesis of Compound B: In the following discussion, Compound A is
3,4-dihydroxy-thiophene-2,5-dicarboxylic acid dimethyl ester; and
Compound B is 3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene-2,5-dicarboxylic
acid dimethyl ester.

[0058]In this method, 3,4-dihydroxy-thiophene-2,5-dicarboxylic acid
dimethyl ester, the thiophene derivative labeled A in FIG. 9 (hereinafter
referred to as Compound A) is first synthesized from commercially
available chemicals according to prior art techniques (see K. Zong, L.
Madrigal, L. B. Groenendaal, R. Reynolds, Chem. Comm., 2498, 2002). Then,
a solution of Compound A, 2,2,2-trifluoroethanol, PPh3, and DEAD is
refluxed in THF for about 15-24 hours (preferably under an inert
atmosphere). The reaction mixture is evaporated to dryness. The resulting
material is loaded into a silica gel column and eluded by hexane and
dichloromethane (4:1, 2:1, 1:1, volume ratio) to yield
3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene-2,5-dicarboxylic acid dimethyl
ester, the thiophene derivative labeled B in FIG. 5 (hereinafter referred
to as "Compound B").

[0059]A yield of 25% for Compound B was obtained using the following
reaction parameters: 3.00 g, (12.92 mmol) of Compound A; 2.84 g (2.2 eq)
of 2,2,2-trifluoroethanol; 7.46 g (2.2 eq) of PPh3; 5.00 ml (2.45
eq) of DEAD; and 45 ml of THF. An Argon reflux for 21 hours generated
1.30 g of Compound C (a white solid), which is equal to a product yield
of about 25%.

[0060]Synthesis of Compound C: In this discussion, Compound C is
3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene-2,5-dicarboxylic acid.

[0061]Next, a quantity of Compound B is dissolved in a solution of sodium
hydroxide and ethanol and stirred for about 12-20 hours (preferably under
an inert atmosphere) while maintaining a constant temperature of about
50-70° C. The resulting solution is cooled, and any excess sodium
hydroxide is neutralized using concentrated hydrochloric acid (not
specifically identified in FIG. 9). The reaction product is collected
using an ether extraction and purified by loading the product into a
silica gel column and eluding using hexane and ethyl acetate (1:1, 1:2,
volume ratio). This procedure yields
3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene-2,5-dicarboxylic acid, the
thiophene derivative labeled C in FIG. 9 (hereinafter referred to as
Compound C).

[0062]A yield of about 51% for Compound C was obtained using the following
reaction parameters: 1.30 g (3.28 mmol) of Compound B was dissolved in a
solution of 1.30 g (32.5 mmol) of sodium hydroxide, and 45 ml of ethanol,
and stirred at 60° C. under Argon for 16 hours. Excess sodium
hydroxide was neutralized using 3 ml of concentrated HCl. The product was
collected using the ether extraction and elution techniques noted above,
yielding about 0.62 g of Compound C, which is equal to a product yield of
about 51%.

[0063]Synthesis of Compound D: In the following discussion, Compound D is
3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene.

[0064]A quantity of Compound C is dissolved in quinoline and a barium
promoted copper chromite catalyst is added. Those of ordinary skill in
the art will recognize that "barium promoted" refers to the incorporation
of small amounts of barium in a catalyst, to increase the performance of
the catalyst. Barium promoted copper chromite catalyst is available from
Strem Chemicals, Inc. of Newburyport, Mass. The chemical formula of the
barium promoted copper chromite catalyst is as follows: 62-64%
Cr2CuO4, 22-24% CuO, 6% BaO, 0-4% Graphite, 1% CrO3, and
1% Cr2O3. The solution of quinoline and the barium promoted
copper chromite catalyst is labeled Cu/Cr in FIG. 9 (hereinafter referred
to as solution Cu/Cr). The solution of Compound C and solution Cu/Cr is
heated to about 170-190° C. for about 12-18 hours (preferably
under an inert atmosphere). The reaction mixture is cooled, and then, the
reaction product is extracted using an ether workup (those of ordinary
skill in the art will recognize that such an ether workup is a common
technique in organic chemical synthesis and need not be described in
greater detail). The extracted reaction product is dried over magnesium
sulfate and purified using a silica gel column and elution with hexane
and dichloromethane (1:1, volume ratio), yielding the fluorinated EC
monomer 3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene (labeled D in FIG. 9
and corresponding to Compound D as used herein), a white solid.

[0065]A yield of 42% for the fluorinated EC monomer
3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene (Compound D) was obtained
using the following reaction parameters: 0.62 g (1.68 mmol) of Compound C
was dissolved in 3.5 ml of quinoline, with 0.15 g of barium promoted
copper chromite catalyst, and heated to 150° C. for 15 hours under
an Argon (inert) atmosphere. The reaction mixture was cooled, and the
product was collected using the ether extraction and elution techniques
noted above, yielding 0.200 g of Compound D, which is equal to a product
yield of about 42%.

[0066]Synthesis of Compound E: In the following discussion, Compound E is
2,5-dibromo-3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene.

[0067]A quantity of Compound D is dissolved in a mixture of chloroform,
acetic acid, and NBS (N-bromosuccinimide), and the resulting mixture is
stirred at room temperature for a period of time (about 2-5 hours). The
solution of Compound D is heated to boiling for about 15-45 minutes
(preferably under an inert atmosphere). The reaction mixture is cooled,
and then, the reaction product is extracted using an aqueous workup
(those of ordinary skill in the art will recognize that such an aqueous
workup is a common technique in organic chemical synthesis and need not
be described herein in greater detail). The extracted reaction product is
dried over magnesium sulfate and purified using a silica gel column and
elution with hexane and ethyl acetate (5:1, volume ratio), yielding
2,5-dibromo-3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene (labeled E in FIG.
9, hereafter referred to as Compound E), a white crystalline solid.

[0068]A yield of about 54% for Compound E was obtained using the following
reaction parameters: A solution of Compound D (1.48 g, 5.28 mmol) and NBS
(2.35 g, 11.62 mmol) in chloroform (70 ml)/acetic acid (70 ml) was
stirred at room temperature for three hours. Then, the mixture was
refluxed under Argon (inert) for 30 minutes. After cooling, the reaction
mixture was filtered with an aqueous workup. The solution was dried over
magnesium sulfate. Chromatography was performed using a silica gel column
with hexane/ethyl acetate (5:1 volume ratio) as solvent. About 1.26 g of
white crystal was obtained, which is equal to a product yield of about
54%.

[0069]Synthesis of Compound 1: In the following discussion, Compound 1 is
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene.

[0070]A final synthesis step for producing Compound 1 involves refluxing a
mixture of Compound E, 2-tributyltin thiophene, and
dichlorobis(triphenylphosphine) Palladium (II) in tetrahydrofuran until
the reaction is complete, as indicted by monitoring the reaction mixture
using a technique such as Thin Layer Chromatography (TLC). The reaction
mixture is loaded directly into a silica gel column and eluded using
hexane/ethyl acetate (4:1 volume ratio) as solvents, yielding
quantitative amounts of a slightly yellow crystal, Compound 1 (i.e.,
2,5-di(thien-2-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene).

[0071]Compound 1 was obtained using the following reaction parameters: a
solution of Compound E (0.300 g, 0.685 mmol), 2-tributyltin thiophene
(0.562 g, 1.51 mmol), and dichlorobis(triphenylphosphine) Palladium (II)
(0.5 mol %) in tetrahydrofuran (15 mL) was refluxed under Argon (inert).
The reaction was monitored by TLC and was finished after 15 hours. The
reaction mixture was loaded on a silica gel column directly using
hexane/ethyl acetate (4:1 volume ratio) as a solvent. About 0.30 g of
slightly yellow crystal was obtained. The yield was quantitative.

[0072]It should be noted that the synthesis shown in FIG. 9 can be easily
modified to achieve other fluorinated EC monomers simply by replacing
2,2,2-trifluoroethanol (used to convert Compound A to Compound B) with
appropriate other fluorinated alcohols, such as 2-fluoroethanol,
2,3,4,5,6-pentfluorobenzyl alcohol, and 2,2-difluoro-1,3-propanediol.
Using the synthesis shown in FIG. 9, other fluorine containing EC
monomers can be produced.

[0073]Starting from the production of Compound E, an alternative synthesis
is as follows. A solution of Compound D (FW 280.19, 1.48 g, 5.28 mmol)
and NBS (FW177.99, 2.35 g, 2.5 eq) in chloroform (70 ml) and acetic acid
(70 ml) was stirred at room temperature for 16 hours. The solution was
then refluxed for 30 minutes. The reaction mixture was poured into water
and extracted using methylene chloride. The resulting reaction product
(Compound E) was dried over magnesium sulfate and purified using
chromatography purification. 1.26 g of white crystal was obtained. The
yield was 54%.

[0075]FIG. 10A schematically illustrates the synthesis of Compound 3, the
structure of which is illustrated in FIG. 7c, which may potentially be
employed as a green EC polymer.

[0076]Synthesis of Compound 3: In the following discussion, Compound 3 is
2,5-(2,3-dihydro-thieno
[3,4-b][1,4]dioxin-5-yl)-3,4-di(2,2,2-trifluoro-ethoxy)-thiophene.

[0077]Compound E is first synthesized as described above in connection
with FIG. 9. A solution of Compound E, 2-tributyltin-3,4-ethylenedioxyl
thiophene, dichlorobis(triphenylphosphine) Palladium (II) is refluxed in
THF under an inert atmosphere for about 14-20 hours. The reaction mixture
is loaded into a silica gel column and eluded by hexane/ethyl acetate
(10:1, 7:1, 4:1), yielding a colorless oil (i.e., Compound
3,2,5-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-3,4-di(2,2,2-trifluoro--
ethoxy)-thiophene).

[0078]A yield of about 27% for Compound 3 was obtained using the following
reaction parameters. A solution of Compound E (0.300 g, 0.685 mmol) and
2-tributyltin-3,4-ethylenedioxyl thiophene (0.650 g, 1.51 mmol),
dichlorobis(triphenylphosphine) Palladium (II) (0.5 mol %) in THF (15 mL)
was refluxed under Argon (inert) for 17 hours. The reaction mixture was
loaded on a silica gel column and eluded by hexane/ethyl acetate (10:1,
7:1, 4:1). 0.103 g of colorless oil was obtained. The yield was about
27%.

[0079]FIG. 10B is a UV-Vis spectra of Compound 3 in a 0.1 M LiClO4
solution of acetonitrile.

[0081]It should be noted that the synthesis shown in FIG. 10A can be
easily modified to achieve other fluorinated EC monomers, simply by using
replacing 2,2,2-trifluoroethanol (used to convert Compound A to Compound
B; see FIG. 9) with appropriate other fluorinated alcohols, such as
2-fluoroethanol, 2,3,4,5,6-pentfluorobenzyl alcohol, and
2,2-difluoro-1,3-propanediol. This modification will result in a
different Compound E, the starting material for the synthesis in FIG.
10A.

[0082]Thus, the starting material would be:
2,5-dibromo-3,4-bis-(RO)-thiophene (i.e., a fluorinated derivative of
2,5-dibromo-3,4-dihydroxy-thiophene) rather than
2,5-dibromo-3,4-bis-(2,2,2-trifluoro-ethoxy)-thiophene, where R--OH is
the fluorinated alcohol replacing 2,2,2-trifluoroethanol.

[0084]FIG. 11B illustrates the structures of six derivatives that were
synthesized based on the compounds of FIG. 11A, respectively labeled
Compounds 10-15. Empirical studies indicated that Compounds 13 and 14
exhibit saturated green colors in the reduced states and are
substantially transparent in the oxidized state. Based on the studies
noted above, it was determined that Compound 13 warranted further study.

Exemplary Synthesis of Compound 13 (FIG. 11B)

[0085]FIG. 12 schematically illustrates the synthesis of Compound 13 of
FIG. 11B, which may potentially be employed as a green EC polymer once it
has been polymerized.

[0086]Synthesis of Compound 13: In the following discussion, Compound 13
is: 2,3-dibenzyl-5,7-di(thien-2-yl) thieno[3,4-b]pyrazine.

[0087]In this synthesis, 2,5-dibromo-3,4-dinitro-thiophene (Compound A)
and 2-tributyltim-thiophene are combined in the presence of a palladium
catalyst (such as dichlorobis(triphenylphosphine) Palladium (II)), to
obtain 2,5-di(thien-2-yl)-3,4-dinitro-thiophene (Compound B).

[0088]In the presence of tin and hydrochloric acid, Compound B is
converted to 2,5-di(thien-2-yl)-3,4-diamino-thiophene (Compound C).

[0089]Then, a solution of Compound C (0.300 g, 1.08 mmol), benzil (0.227
g, 1.08 mmol), and p-toluene sulfonate acid (9 mg, 5 mol %) in chloroform
(20 mL) was refluxed under Argon (inert) for 17 hours. The reaction
mixture was evaporated and the residue was loaded into a silica gel
column. Methylene chloride/hexane (1:1) was used to elude the compound.
About 0.350 g of purple solid was obtained. The yield was thus about 72%.

Exemplary Polymerization Techniques

[0090]One aspect of the present disclosure is directed to a method for
producing EC polymer films using electropolymerization. Two related
electropolymerization techniques can be employed to polymerize EC
monomers in order to achieve a high quality EC polymer film. Density is
required to achieve the high contrast between the bleached and unbleached
states. High quality is required for repeatability over many cycles. EC
polymer films that do not exhibit high contrast and repeatability over
many cycles are not very useful as components in EC polymer-based
devices, such as windows and displays.

[0091]EC polymer films were produced based on Compound 1, Compound 3, and
Compound 13. Specific parameters of these polymerizations are described
below. An overview of the two basic electropolymerization techniques is
described as follows.

[0092]A first electropolymerization technique is summarized in a flow
chart 200 in FIG. 13. EC monomers are prepared in a block 202, and then
cyclic voltammetry is employed, as indicated in a block 204, to
polymerize the EC monomer and to deposit the resultant polymer as a film
on a substrate, preferably an indium tin oxide (ITO) coated transparent
substrate.

[0093]The second electropolymerization technique in accord with the
present invention is summarized in a flow chart 212 in FIG. 14. Once
again, EC monomers are prepared in a block 214 (as described above). Once
the starting monomer is obtained or prepared, the monomer is polymerized
first using chronoamperometry, as indicated in a block 216, followed by
cyclic voltammetry, as indicated in a block 218. The second
electropolymerization technique combining both chronoamperometry and
cyclic voltammetry appears to achieve a higher quality, more durable EC
polymer film.

[0094]Referring now to block 216 of FIG. 14, the first step in the two
part electropolymerization of the EC monomer can be achieved using
chronoamperometry under the following conditions. Oxidative
electrochemical polymerization of the monomer is initiated using
chronoamperometry to deposit a very thin, very uniform layer of EC
polymer onto an ITO coated glass substrate using a platinum wire as a
counter electrode. Once again, the selected monomer is placed into a
solvent/salt solution, such as a propylene carbonate solution with
tetrobutylammonium perchlorate salt.

[0095]In a block 218, multiple scan cyclic voltammetry is employed to
deposit additional polymer onto the uniform layer deposited using
chronoamperometry. Additional cycles may be required for the deposition
of an acceptably dense layer of polymer.

Exemplary Polymerization of Compounds 1 and 3

[0096]The following technique was used to successfully achieve a stable
polymer based on Compound 1. Compound 1 (22 mg) and lithium perchlorate
(53 mg) are dissolved in acetonitrile (5.0 ml). The resulting solution
contains 0.01 M of Compound 1 and 0.10 M of lithium perchlorate. The
solution is purged by Argon for 15 minutes before electrochemical
polymerization. A potentiostat and three electrode setups are used with
ITO as working electrode, platinum wire as a counter electrode, and
silver wire as a reference electrode. The electrodes are cleaned and
dried carefully prior to use. The polymerization can be done in two ways.
The first approach is by applying the cyclic voltammetry method. The
parameters include a scanning range of -0.1 volts to 1.1 volts, and a
scanning rate of 50 mV/s for 10 cycles. The second approach is carried
out by applying chronoamperometry. The potential applied is 1.2 volts for
20 s (versus an Ag reference electrode).

[0097]The same technique can be used to polymerize Compound 3.

Exemplary Polymerization of Compound 13

[0098]The following technique was used to successfully achieve a stable
polymer based on Compound 13. Compound 13 (23 mg) and tetrabutylammonium
hexafluorophosphate (193 mg) are dissolved in methylene chloride (2.5 ml)
and acetonitrile (2.5 ml). The resulting solution contains 0.01 M of
Compound 13 and 0.10 M of tetrabutylammonium hexafluorophosphate. The
solution is purged by Argon for 15 minutes before electrochemical
polymerization. A potentiostat and three electrode setups are used with
ITO as the working electrode, a platinum wire as a counter electrode, and
a silver wire as a reference electrode. The electrodes are carefully
cleaned and dried prior to use. Cyclic voltammetry is used for
polymerization. The parameters include a scanning range of -0.05 to 0.85
volts (versus an Ag reference electrode), and a scanning rate of 20 mV/s
for 8 cycles.

Exemplary EC Devices Including Green EC Polymers

[0099]FIG. 15 schematically illustrates an EC device including a green EC
polymer, such as Compounds 1, 3, or 13, as discussed in detail above. A
first layer is implemented by ITO transparent electrode 12, followed by
an insulating layer 14 (which can be implemented using a non-conductive
and transparent polymer such as a parafilm). A reference electrode 18
(preferably implemented using a silver electrode) is sandwiched between
upper and lower insulating layers 14. A layer of a green EC polymer 11 is
sandwiched between lower insulating layer 14 and a lower transparent
electrode 12. Note that each insulating layer includes an opening 20,
which is filled with an electrolyte 16. The openings enable electrical
charges to be exchanged between the transparent electrodes, the reference
electrode, the electrolyte, and the green EC polymer.

[0100]A plurality of different electrolytes can be employed. An important
component of an EC device is the electrolyte, which must be ionically
conductive, but electronically insulating. The use of a semi-solid (or
gel) electrolyte is preferred. Such gel electrolytes generally are formed
by combining an alkali metal salt (a source of ions) with a polymer host
(for stability). For a gel electrolyte to be suitable for smart windows
or smart displays, it is important that the gel electrolyte provide high
ionic conductivity, high light transmittance (i.e., be optically clear),
and be stable over a wide range of time and temperatures. High ionic
conductivity is essential in an EC device, because the ions need to
freely and quickly migrate within the polymer matrix. Electric
conductivity should be negligible, so that the device does not short
circuit. For smart window applications, a high light transmittance is
also important to maximize the transparency of the window in the bleached
state.

[0101]Stability is equally vital in an EC device. There should be a
minimal change in conductivity and transmittance for gel electrolytes
measured over time and at various temperatures. These parameters can
vary, depending on the salt and solvent combinations used.

[0102]In general, gel electrolytes offer superior conductivity compared to
entirely solid polymer electrolytes. While liquid electrolytes can be
employed, gel electrolytes offer the advantages of mechanical stability
(thus facilitating leak-free devices), low weight, and established
lifetimes of at least 50,000 cycles, as empirically determined. In a gel
electrolyte, the solid polymer matrix of polyvinyl chloride (PVC) and
polymethylmethacrylate (PMMA) provides dimensional stability to the
electrolyte, while the high permittivity of the solvents enables
extensive dissociation of the lithium salts. The low viscosity of the
solvents provides an ionic environment that facilitates high ionic
mobility. A variety of different combinations of salts and solvents have
been studied to determine optimum combinations.

[0103]Highly conductive gel electrolytes have been synthesized from a salt
dissolved in an electrolyte solution with the polymer matrix, with PMMA
added for dimensional stability. Lithium (Li) is commonly used as the
salt in EC switching devices due to its small size and because it
facilitates the reduction and oxidization of EC polymers. Another salt,
tetrabutyl ammonium phosphate (TBAP), can also be employed. Overall, the
salt must have a high degree of dissociation and the anion must have a
high level of charge delocalization so that the ion-pairing is minimized.

[0104]An exemplary, but not limiting list of possible salts includes
lithium perchlorate (LiClO4), tetrabutyl ammonium perchlorate
(TBAP), and trifluorosulfonimide (LiN(CF3SO2)2. An
exemplary, but not limiting list of solvents includes propylene carbonate
(PC), ethylene carbonate (EtC), acetonitrile (ACN), and
γ-butyrolactone (GBL). Preferably, solvents are substantially dried
over molecular sieves before their use. In general, gel electrolytes are
synthesized by first dissolving the salt in the solvent, and then adding
the PMMA. A highly conductive (2 mS/cm), viscous and transparent (88%)
gel electrolyte can generally be achieved in this manner.

[0105]Still another useful gel electrolyte can be prepared from 3%
LiClO4, 7% PMMA, 20% PC, and 70% acetonitrile (ACN) (% by weight). A
simple synthesis of such a gel was achieved by first dissolving the PMMA
and LiClO4 in ACN. The PC was dried over 4 angstrom molecular sieves
and then combined with the other ingredients. The complete mixture was
stirred for 10-14 hours at room temperature. A high conductivity (2
mS/cm), high viscosity, and transparent gel electrolyte was thus formed.
As described above, the solid polymer matrix of PMMA provides dimensional
stability to the electrolyte, while the high permittivity of the solvents
PC and ACN enable extensive dissociation of the lithium salt. The low
viscosity of PC provides an ionic environment that facilitates high ionic
mobility.

[0106]While gel electrolytes are preferred because they facilitate the
production of a solid state device (the solvent liquid is contained
within the polymer matrix), liquid electrolytes can be used in an EC
device. One such liquid electrolyte can be achieved, for example, using
0.1 M tetrabutylammonium perchlorate (TBAP) in ACN. It is contemplated
that materials other than PVC and PMMA can be employed to provide a
polymer matrix for a gel electrolyte, and that materials other than TBAP
and LiClO4 can be employed as ionic sources. It should be noted that
in the context of the present technology, the terms "gel electrolyte" and
"solid electrolyte" are use synonymously, because the liquid materials
employed in fabricating a gel electrolyte are absorbed in a polymer
matrix, and there are substantially no free liquids that are not
contained within the polymer matrix.

[0107]A second exemplary EC device including a green EC polymer is
schematically illustrated in a transparent state 50a in FIG. 16A, and in
a colored state 50b in FIG. 16B. From a structural standpoint, there is
no difference in the EC device when in its transparent state or its
colored state. The second exemplary EC device, as illustrated in both of
its states in FIGS. 16A and 16B, includes a green EC polymer layer and a
counter-electrode layer. Again, the top layer is transparent electrode
42, again, preferably ITO. The next layer is the green EC polymer, which
in FIG. 16A is shown as a non-green layer 44a (this layer could be
transparent, as with Compound 13, or red, as with Compound 1), and in
FIG. 16B is shown as a colored layer 44b (in the reduced state the green
EC polymers discussed above exhibit a saturated green color). Next to the
EC polymer layer is a solid/gel electrolyte layer 46. The solid
electrolyte layer is followed by a counter-electrode layer 52. No bottom
transparent electrode layer is required or included.

[0108]Counter-electrode layer 52 is preferably gold-based, platinum-based,
or highly conductive carbon-based, or vanadium pentoxide-based. A
preferred highly conductive carbon is graphite. It should be understood
that while graphite certainly represents a preferred highly conductive
carbon, other highly conductive carbon materials can instead be
beneficially employed as a conductive film applied as a coating on a
transparent substrate to produce a counter-electrode. Many types of
conductive carbons are available from a variety of manufacturers, such as
Tokai Carbon Co. of Tokyo, Japan; and Loresco International, of
Hattiesburg, Miss. Thus, the use of the term "graphite" herein should be
considered to be exemplary, rather than limiting on the scope of the
present technology. It is further contemplated that nickel can be
beneficially employed as a conductive film on a transparent substrate, to
produce a counter-electrode. The use of a counter-electrode can improve
the speed of the color change between states, as well as improve the
contrast ratio between the two states. The counter-electrode material
should be chemically stable, provide high electrical conductivity, and
should be easy to fashion into a patterned substrate. Gold, highly
conductive carbons, and platinum have been identified as electrically
conductive materials that can be beneficially employed for making a
counter-electrode. It is contemplated that graphite will be very useful
because of its low cost. Gold, while much more expensive, can be used in
very thin layers, thereby minimizing the cost of a gold-based
counter-electrode. Platinum, while electrically conductive, is likely to
be so expensive as to preclude its use. It is further contemplated that
still other conductive materials can be employed to produce the
counter-electrode.

[0109]Although the concepts disclosed herein have been described in
connection with the preferred form of practicing them and modifications
thereto, those of ordinary skill in the art will understand that many
other modifications can be made thereto within the scope of the claims
that follow. Accordingly, it is not intended that the scope of these
concepts in any way be limited by the above description, but instead be
determined entirely by reference to the claims that follow.